My mother passed away on 24 Shevat 5776. There were 2 months of Adar in that year so when is the last day I say Kaddish?
One recites kaddish for 11 months no matter whether it is a regular or a leap year. Thus, in a leap year, one stops saying kaddish two months before the calendar date.
26:17 The custom is to say Kaddish for only eleven months so as not to suggest that one’s parent was an evil person. This is because the evil are judged for twelve months. Therefore, if a person dies on the tenth day of the month of Shevat, Kaddish is recited until the ninth of Teves. Kaddish is not recited on the tenth of Teves, which is the first day of the twelfth month. For this purpose, we count from the burial and not from the date of the deceased passing because one’s judgment does not commence until the burial. Therefore, if one was buried on the eleventh of Shevat, Kaddish stops on the tenth of Teves; in a leap year, Kaddish would stop on the appropriate date in Kislev.